1. Field of the Invention
The present invention relates to a transfer apparatus primarily for transferring an article which is worn such as a disposable diaper or a sanitary napkin.
2. Description of the Related Art
In order to transfer an article of this type from another apparatus in a preceding stage, typically a negative pressure is created using air so as to attract the article onto an attracting pad (e.g., Japanese Laid-Open Patent Publication No. 63-317576).
The attracting pad attracts a front portion of the article and then attracts a rear portion of the article. The present inventors have noticed that all of the suction holes of the attracting pad are open when attracting the front portion of the article, whereby there is a suction loss if one attempts to obtain a sufficient attracting force. The present inventors have also noticed that when attracting the rear portion of the article, since some of the suction holes are already covered by the article, the attracting force may be excessive, which may result in wrinkles in the article.
An article transfer apparatus is provided which is capable of reliably attracting the article with a sufficient attracting force and yet has a reduced suction loss.
The present invention provides a transfer apparatus, including: an attracting pad including a front attracting section and a rear attracting section each having suction holes for applying a negative pressure, which is created through suction of air, on an article; and a moving section for moving the attracting pad, whereby the attracting pad attracts a front portion of the article by air and then attracts a rear portion of the article by air so as to pick up the article from another apparatus in a preceding stage and to transfer the article that has been picked up, wherein an air suction amount (the amount of air that is sucked) through the front attracting section is set to be greater than an air suction amount through the rear attracting section when a negative pressure is applied on the suction holes in a non-attracting state where the attracting pad is not attracting the article.
When the pad attracts the front portion of the article, the suction holes of the front and rear attracting sections are open, whereby the suction through the rear attracting section is a loss. However, the suction loss is reduced because the suction amount through the rear attracting section is smaller than the suction amount through the front attracting section. Moreover, since the suction amount through the front attracting section is greater, and thus the attracting force thereof is greater, the reliability of the attraction operation is improved in the beginning of the operation of attracting the article.
On the other hand, after the front portion of the article has been attracted, since the suction holes of the front attracting section are covered by the article, the attraction of the article increases the suction amount through the rear attracting section relative to the suction amount through the front attracting section, whereby a sufficient attracting force can be obtained also in the rear attracting section.
Herein, the term xe2x80x9csuction holexe2x80x9d may refer to a hole opened in the attracting surface of the attracting pad, or an equivalent thereof.
The term xe2x80x9cfront attracting sectionxe2x80x9d may refer to a section that attracts the article first or earlier than another section, or an equivalent thereof, and xe2x80x9crear attracting sectionxe2x80x9d may refer to a section that attracts the article last or later than another section, or an equivalent thereof.
Herein, the phrase xe2x80x9cthe suction amount through the front attracting section is set to be greater than the suction amount through the rear attracting sectionxe2x80x9d may mean that the air suction resistance through the front attracting section is set to be smaller than the air suction resistance through the rear attracting section when a negative pressure is applied on the suction holes in a non-attracting state where the attracting pad is not attracting the article.
The air suction resistance through the front attracting section (rear attracting section) decreases as the number and the area (cross-sectional area) of the suction holes provided in the front attracting section (rear attracting section) increase, and increases as the length of each suction hole increases.
A specific method of setting the suction amounts as described above is to set the total cross-sectional area of the suction holes of the front attracting section to be greater than that of the rear attracting section.
Herein, the term xe2x80x9ccross-sectional area of a suction holexe2x80x9d may refer to the area of the suction hole along a cross section thereof that is perpendicular to the axial line of the suction hole, and it generally coincides with the area of the opening of the suction hole on the attracting surface of the pad. However, when the axial line of the suction hole is not perpendicular to the attracting surface, the cross-sectional area of the suction hole is smaller than the area of the opening thereof. Moreover, when the suction hole is tapered so as to expand in the vicinity of the attracting surface, the cross-sectional area of the suction hole is smaller than the area of the opening thereof.
It is typically preferred that the cross-sectional shape of a suction hole is a circular shape. However, it may alternatively be an elliptical shape, a rectangular shape, a polygonal shape, or the like. It may even be an oval shape or a slit-like shape (groove-like shape). Moreover, while it is typically preferred that the number of suction holes is more than one, it may alternatively be one if the suction hole has a slit-like shape.
In a case where a plurality of suction holes are provided in each of the front and rear attracting sections, it is typically preferred that the number of suction holes in the front attracting section is greater than the number of suction holes in the rear attracting section. However, the same number of suction holes may alternatively be provided in the front attracting section and in the rear attracting section.
Based on the above, the suction amount through the front attracting section can be set to be greater than the suction amount through the rear attracting section in one of the following manners, for example:
(1) Provide the same number of suction holes in the front attracting section and in the rear attracting section, with the cross-sectional area of the suction holes in the front attracting section being greater than that in the rear attracting section;
(2) Set the cross-sectional area of the suction holes in the front attracting section to be substantially the same as that in the rear attracting section, with the number of suction holes in the front attracting section being greater than that in the rear attracting section;
(3) Set the number and the cross-sectional area of the suction holes in the front attracting section to be greater than those in the rear attracting section; and
(4) Set the cross-sectional area of the air suction path communicated to the suction holes in the front attracting section to be greater than that in the rear attracting section. The air suction resistance can be adjusted by providing an orifice along the air suction path.
Herein, the term xe2x80x9carticlexe2x80x9d may refer primarily to a worn article. Herein, the term xe2x80x9cworn articlexe2x80x9d is a concept encompassing a multilayer material made of at least one of a nonwoven, a fabric and a fiber, a single layer fabric or nonwoven, and the like, including a finished or semi-finished product of a sanitary napkin, a disposable diaper, or disposable pants. Herein, the term xe2x80x9cnonwovenxe2x80x9d includes staple nonwoven, filament nonwoven, wetlaid nonwoven, drylaid nonwoven, airlaid nonwoven, airlaid pulp nonwoven, carded nonwoven, parallel-laid nonwoven, cross-laid nonwoven, randomlaid nonwoven, spunlaid nonwoven, meltblown nonwoven, and the like. Methods for manufacturing a disposable worn article while changing the interval between semi-finished products of the disposable worn article are disclosed in, for example, Japanese Laid-Open Patent Publication No. 64-38377, Japanese Laid-Open Patent Publication No. 3-176053, Japanese Laid-Open Patent Publication No. 4-161152, and U.S. Pat. No. 5,660,657, which are incorporated herein by reference.
In a case where the orientation of pads changes, the interval between the pads transferring semi-finished products thereon also changes.